iBGP sync

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Learn about the components of BGP that govern route eligibility due to next-hop reachability. Learn how synchronization functions inside of BGP and how it affects routes being installed into the routing table.

- [Voiceover] For BGP to consider a route valid,…it needs to have a next hop address for that route,…reachable via the routing table.…This can be done via recursive lookup, direct route,…or being directly connected.…If a next hop address is not reachable,…then the route is invalid and can't be installed…into the routing table.…In this diagram, I avoided this issue with the route source…via ISPs by redistributing the static route…to one dot one dot one dot three via OSPF.…Examining router two's route table,…show IP route, pipe, include one dot one dot one dot three.…

I see that route's destined to exit via ISP one,…have a next hop set to one dot one dot one dot three.…We'll now remove static redistribution from router one.…Router OSPF ten.…No redistribute static.…Back to router two, and I see both the OSPF route is gone,…along with the BGP route.…Using show IP BGP, ten dot 100 dot zero dot zero,…gives the full story.…

While the path shown…for one dot one dot one dot three is shorter,…next hop address one dot one dot one dot three…

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Released

6/5/2018

Earning the Cisco CCNP Routing and Switching certification indicates that you have the skills needed to plan, verify, and troubleshoot enterprise networks. In this course, instructor Greg Sowell prepares you for exam 300-101 ROUTE, Implementing Cisco IP Routing—a qualifying exam for the CCNP Routing and Switching certification—by reviewing essential internet connectivity concepts that are covered on the exam. Greg covers how to configure a Dynamic Host Configuration Protocol (DHCP) client and discusses how Port Address Translation (PAT) is utilized to allow many internal clients to NAT to a single IP address. He also goes over internet routing, discussing iBGP and eBGP concepts.